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DOE OSTI2020

MoorDyn V2: New Capabilities in Mooring System Components and Load Cases

MoorDyn, an open-source mooring dynamics model, is being expanded with capabilities for additional mooring system features and load cases. As floating wind turbine technology matures, mooring systems are becoming more sophisticated and more complex scenarios need to be considered in the design process. Mooring systems may have synthetic line materials, ballast/buoyancy bodies along the lines, or interconnections between platforms. Failure modes may involve multiple cascading line failures that depend on mooring system dynamics. Features recently added to MoorDyn aim to address these emerging needs. MoorDyn’s linear elasticity model has been supplemented to support user-defined stress-strain curves, which can be adjusted to represent synthetic mooring materials. Rigid six-degree-of-freedom bodies in the mooring system can now be modeled using two new model objects. “Rod” objects provide an option for rigid cylindrical bodies. They use the existing Morison equation-based hydrodynamics model and can be connected to mooring lines at either end. “Body” objects provide a generic six-degree-of-freedom rigid-body representation based on a lumped-parameter model of translational and rotational properties. Rod objects can be added to Body objects and mooring lines can be attached at any location, allowing a wide variety of submerged structures to be integrated into the mooring system. Lastly, a means of dynamically simulating mooring line failures has been implemented. These new features, currently in the C++ version of MoorDyn, are described and then demonstrated on a two-turbine shared-mooring array. A qualitative view of the results suggests the new features are functioning as expected.

49 EE - Wind and Water Power Program - Wind (EE-4W↗

DOE OSTI2020

MoorDyn V2: New Capabilities in Mooring System Components and Load Cases: Preprint

49 EE - Wind and Water Power Program - Wind (EE-4W↗

DOE OSTI2014

THE IMPORTANCE OF THE MAGNETIC FIELD FROM AN SMA-CSO-COMBINED SAMPLE OF STAR-FORMING REGIONS

Submillimeter dust polarization measurements of a sample of 50 star-forming regions, observed with the Submillimeter Array (SMA) and the Caltech Submillimeter Observatory (CSO) covering parsec-scale clouds to milliparsec-scale cores, are analyzed in order to quantify the magnetic field importance. The magnetic field misalignment δ—the local angle between magnetic field and dust emission gradient—is found to be a prime observable, revealing distinct distributions for sources where the magnetic field is preferentially aligned with or perpendicular to the source minor axis. Source-averaged misalignment angles (|δ|) fall into systematically different ranges, reflecting the different source-magnetic field configurations. Possible bimodal (|δ|) distributions are found for the separate SMA and CSO samples. Combining both samples broadens the distribution with a wide maximum peak at small (|δ|) values. Assuming the 50 sources to be representative, the prevailing source-magnetic field configuration is one that statistically prefers small magnetic field misalignments |δ|. When interpreting |δ| together with a magnetohydrodynamics force equation, as developed in the framework of the polarization-intensity gradient method, a sample-based log-linear scaling fits the magnetic field tension-to-gravity force ratio (Σ {sub B}) versus (|δ|) with (Σ {sub B}) = 0.116 · exp (0.047 · (|δ|)) ± 0.20 (mean error), providing a way to estimate the relative importance of the magnetic field, only based on measurable field misalignments |δ|. The force ratio Σ {sub B} discriminates systems that are collapsible on average ((Σ {sub B}) < 1) from other molecular clouds where the magnetic field still provides enough resistance against gravitational collapse ((Σ {sub B}) > 1). The sample-wide trend shows a transition around (|δ|) ≈ 45°. Defining an effective gravitational force ∼1 – (Σ {sub B}), the average magnetic-field-reduced star formation efficiency is at least a factor of two smaller than the free-fall efficiency. For about one fourth of the sources the average efficiency drops to zero. The force ratio Σ {sub B} can further be linked to the normalized mass-to-flux ratio, yielding an estimate for the latter one without the need of field strength measurements. Across the sample, a transition from magnetically supercritical to subcritcal is observed with growing misalignment (|δ|)

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2016

THE CARMA PAIRED ANTENNA CALIBRATION SYSTEM: ATMOSPHERIC PHASE CORRECTION FOR MILLIMETER WAVE INTERFEROMETRY AND ITS APPLICATION TO MAPPING THE ULTRALUMINOUS GALAXY ARP 193

Phase fluctuations introduced by the atmosphere are the main limiting factor in attaining diffraction limited performance in extended interferometric arrays at millimeter and submillimeter wavelengths. We report the results of C-PACS, the Combined Array for Research in Millimeter-Wave Astronomy Paired Antenna Calibration System. We present a systematic study of several hundred test observations taken during the 2009–2010 winter observing season where we utilize CARMA's eight 3.5 m antennas to monitor an atmospheric calibrator while simultaneously acquiring science observations with 6.1 and 10.4 m antennas on baselines ranging from a few hundred meters to ∼2 km. We find that C-PACS is systematically successful at improving coherence on long baselines under a variety of atmospheric conditions. We find that the angular separation between the atmospheric calibrator and target source is the most important consideration, with consistently successful phase correction at CARMA requiring a suitable calibrator located ≲6° away from the science target. We show that cloud cover does not affect the success of C-PACS. We demonstrate C-PACS in typical use by applying it to the observations of the nearby very luminous infrared galaxy Arp 193 in {sup 12}CO(2-1) at a linear resolution of ≈70 pc (0.″12 × 0.″18), 3 times better than previously published molecular maps of this galaxy. We resolve the molecular disk rotation kinematics and the molecular gas distribution and measure the gas surface densities and masses on 90 pc scales. We find that molecular gas constitutes ∼30% of the dynamical mass in the inner 700 pc of this object with a surface density ∼10{sup 4} M{sub ⊙} pc{sup −2}; we compare these properties to those of the starburst region of NGC 253.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2011

Pulsed X-ray Characterization of Stripline Micro-Channel Plate Gated Imager

We report on characterization of x-ray imaging arrays developed by National Security Technologies, LLC. These devices are based on a microchannel plate (MCP) with a conventional glass microchannel structure, but the top and bottom conductive coatings, rather than covering the entire area, are configured into several (4 to 8) parallel strips. Since the bias voltage is a pulse launched from one end, these operate as striplines; relative delays between these pulses give different active exposure times. Unlike the case of a static bias voltage, non-uniformities in impedance along a stripline will produce spatial fluctuations in the bias voltage. These are expected to be slight, but the very sensitive dependence of gain on voltage - approximately like Vl/4d, where l and d are the length and diameter of the channel - means there may be very significant spatial non-uniformities in gain. Flat-field calibrations are therefore required so that such effects can be unfolded from the raw images if quantitative data is required. Such flat-field and other characterization measurements, e.g. responsivity and linearity, have therefore been done with a flash X-ray radiographic system. The maximum endpoint energy is 500 keV. The duration is {approx}40 ns, and so is essentially flat (temporally) during the MCP stripline transit time, which is a maximum of 600 ps. Spatial variations are significant, but the data are corrected using independent flat-field measurements. A monochromator selects a particular X-ray transition line (typically K{alpha}) of the anode material, so that characterizations can be done for various well-defined input photon energies.

47 OTHER INSTRUMENTATION↗

DOE OSTI2017

Piezo-Phototronic Effect on Selective Electron or Hole Transport through Depletion Region of Vis-NIR Broadband Photodiode

Silicon underpins nearly all microelectronics today and will continue to do so for some decades to come. However, for silicon photonics, the indirect band gap of silicon and lack of adjustability severely limit its use in applications such as broadband photodiodes. Here, a high-performance p-Si/n-ZnO broadband photodiode working in a wide wavelength range from visible to near-infrared light with high sensitivity, fast response, and good stability is reported. The absorption of near-infrared wavelength light is significantly enhanced due to the nanostructured/textured top surface. The general performance of the broadband photodiodes can be further improved by the piezo-phototronic effect. The enhancement of responsivity can reach a maximum of 78% to 442 nm illumination, the linearity and saturation limit to 1060 nm light are also significantly increased by applying external strains. The photodiode is illuminated with different wavelength lights to selectively choose the photogenerated charge carriers (either electrons or holes) passing through the depletion region, to investigate the piezo-phototronic effect on electron or hole transport separately for the first time. This is essential for studying the basic principles in order to develop a full understanding about piezotronics and it also enables the development of the better performance of optoelectronics.

36 MATERIALS SCIENCE↗

DOE OSTI2017

Characterization of the macrocyclase involved in the biosynthesis of RiPP cyclic peptides in plants

Enzymes that can catalyze the macrocyclization of linear peptide substrates have long been sought for the production of libraries of structurally diverse scaffolds via combinatorial gene assembly as well as to afford rapid in vivo screening methods. Orbitides are plant ribosomally synthesized and posttranslationally modified peptides (RiPPs) of various sizes and topologies, several of which are shown to be biologically active. The diversity in size and sequence of orbitides suggests that the corresponding macrocyclases may be ideal catalysts for production of cyclic peptides. Here we present the biochemical characterization and crystal structures of the plant enzyme PCY1 involved in orbitide macrocyclization. These studies demonstrate how the PCY1 S9A protease fold has been adapted for transamidation, rather than hydrolysis, of acyl-enzyme intermediates to yield cyclic products. Notably, PCY1 uses an unusual strategy in which the cleaved C-terminal follower peptide from the substrate stabilizes the enzyme in a productive conformation to facilitate macrocyclization of the N-terminal fragment. The broad substrate tolerance of PCY1 can be exploited as a biotechnological tool to generate structurally diverse arrays of macrocycles, including those with nonproteinogenic elements.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2021

Clogging, dynamics, and reentrant fluid for active matter on periodic substrates

Here, we examine the collective states of run-and-tumble active matter disks driven over a periodic obstacle array. When the drive is applied along a symmetry direction of the array, we find a clog-free uniform liquid state for low activity, while at higher activity, the density becomes increasingly heterogeneous and an active clogged state emerges in which the mobility is strongly reduced. For driving along nonsymmetry or incommensurate directions, there are two different clogging behaviors consisting of a drive-dependent clogged state in the low activity thermal limit and a drive-independent clogged state at high activity. These regimes are separated by a uniform flowing liquid at intermediate activity. There is a critical activity level above which the thermal clogged state does not occur, as well as an optimal activity level that maximizes the disk mobility. Thermal clogged states are dependent on the driving direction while active clogged states are not. In the low activity regime, diluting the obstacles produces a monotonic increase in the mobility; however, for large activities, the mobility is more robust against obstacle dilution. We also examine the velocity-force curves for driving along nonsymmetry directions and find that they are linear when the activity is low or intermediate but become nonlinear at high activity and show behavior similar to that found for the plastic depinning of solids. At higher drives, the active clustering is lost. For low activity, we also find a reentrant fluid phase, where the system transitions from a high mobility fluid at low drives to a clogged state at higher drives and then back into another fluid phase at very high drives. We map the regions in which the thermally clogged, partially clogged, active uniform fluid, clustered fluid, active clogged, and directionally locked states occur as a function of disk density, drift force, and activity.

36 MATERIALS SCIENCE↗

DOE OSTI2024

Synergistic Integration of Multiple Wave Energy Converters with Adaptive Resonance and Offshore Floating Wind Turbines through Bayesian Optimization

We developed a synergistic ocean renewable system where an array of Wave Energy Converters (WEC) with adaptive resonance was collocated with a Floating Offshore Wind Turbine (FOWT) such that the WECs, capturing wave energy through the resonance adapting to varying irregular waves, consequently reduced FOWFT loads and turbine motions. Combining Surface-Riding WECs (SR-WEC) individually designed to feasibly relocate their natural frequency at the peak of the wave excitation spectrum for each sea state, and to obtain the highest capture width ratio at one of the frequent sea states for annual average power in a tens of kilowatts scale with a 15 MW FOWT based on a semi-submersible, Bayesian Optimization is implemented to determine the arrangement of WECs that minimize the annual representation of FOWT’s wave excitation spectra. The time-domain simulation of the system in the optimized arrangement is performed, including two sets of interactions: one set is the wind turbine dynamics, mooring lines, and floating body dynamics for FOWT, and the other set is the nonlinear power-take-off dynamics, linear mooring, and individual WECs’ floating body dynamics. Those two sets of interactions are further coupled through the hydrodynamics of diffraction and radiation. For sea states comprising Annual Energy Production, we investigate the capture width ratio of WECs, wave excitation on FOWT, and nacelle acceleration of the turbine compared to their single unit operations. We find that the optimally arranged SR-WECs reduce the wave excitation spectral area of FOWT by up to 60% and lower the turbine’s peak nacelle acceleration by nearly 44% in highly occurring sea states, while multiple WECs often produce more than the single operation, achieving adaptive resonance with a larger wave excitation spectra for those sea states. The synergistic system improves the total Annual Energy Production (AEP) by 1440 MWh, and we address which costs of Levelized Cost Of Energy (LCOE) can be reduced by the collocation.

Engineering↗

DOE OSTI2019

Kiloparsec-Scale Variations in the Star Formation Efficiency of Dense Gas: The Antennae Galaxies (NGC 4038/39)

We study the relationship between dense gas and star formation in the Antennae galaxies by comparing Atacama large millimeter/submillimeter array (ALMA) observations of dense-gas tracers (HCN, HCO{sup +}, and HNC J = 1–0) with the total infrared luminosity (L {sub TIR}) calculated using data from the Herschel Space Observatory and the Spitzer Space Telescope. We compare the luminosities of our star formation rate (SFR) and gas tracers using aperture photometry and employing two methods for defining apertures. We taper the ALMA data set to match the resolution of our L {sub TIR} maps and present new detections of dense-gas emission from complexes in the overlap and western arm regions. Using Owens Valley Radio Observatory CO J = 1–0 data, we compare with the total molecular gas content, M(H{sub 2}){sub tot}, and calculate star formation efficiencies and dense-gas mass fractions for these different regions. We derive HCN, HCO{sup +}, and HNC upper limits for apertures where emission was not significantly detected, because we expect that emission from dense gas should be present in most star-forming regions. The Antennae extends the linear L{sub TIR}--L{sub HCN} relationship found in previous studies. The L{sub TIR}--L{sub HCN} ratio varies by up to a factor of ∼10 across different regions of the Antennae, implying variations in the star formation efficiency of dense gas, with the nuclei, NGC 4038 and NGC 4039, showing the lowest SFE{sub dense} (0.44 and 0.70 × 10{sup −8} yr{sup −1}). The nuclei also exhibit the highest dense-gas fractions (∼9.1% and ∼7.9%).

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2013

NEAR-SURFACE GEOPHYSICAL CHARACTERIZATION OF A HOLOCENE FAULT CONDUCIVE TO GEOTHERMAL FLOW NEAR PYRAMID LAKE, NEVADA

Linear deposits of calcium carbonate tufa columns mark recent faults that cut 11 ka Lake Lahontan sediments at Astor Pass, north of Pyramid Lake, Nevada. Throughout the Great Basin, faults appear to control the location of geothermal resources by providing pathways for fluid migration. Reservoir-depth (greater than 1 km) seismic imaging at Astor Pass reveals a fault that projects to one of the lines of tufa columns at the surface. The presence of the tufa deposits suggests this fault carried warm geothermal waters through the lakebed clay sediments in recent time. The warm fluids deposited the tufa when they hit cold Lake Lahontan water at the lakebed. Lake Lahontan covered this location 11 ka to a depth of at least 60 m. In collaboration with the Pyramid Lake Paiute Tribe, an Applied Geophysics class at UNR investigated the near-surface geophysical characteristics of this fault. The survey at and near the tufa columns comprises near-surface Pwave seismic reflection and refraction, electrical resistivity tomography, nearsurface refraction microtremor arrays, nine near-surface direct-current resistivity soundings, magnetic surveys, and gravity surveys. The refraction microtremor results show shear velocities near tufa and faults to be marginally lower, compared to Vs away from the faults. Overall, the 30-m depth-averaged shear velocities are low, less than 300 m/s, consistent with the lakebed clay deposits. These results indicate that no seismically fast (> 500 m/s) tufa deposits are present below the surface at or near the tufa columns. Vs30 averages were for example 274 ± 13 m/s on the fault, 287 ± 2 m/s at 150 m east of the fault, and 290 ± 15 m/s at 150 m west of the fault. The P-velocity refraction optimization results similarly indicate a lack of high-velocity tufa buried below the surface in the Lahontan sediments, reinforcing the idea that all tufa was deposited above the lakebed surface. The seismic results provide a negative test of the hypothesis that deposition of the lakebeds in the Quaternary buried and preserved older tufa columns within the section. Near-surface Wenner arrays with a-spacings up to 30 m show a higher resistivity near the faults, and tufa, than away from the faults. Resistivity averages within a few meters of the surface were 33 ± 17 ohm-m on the fault, 13 ± 3 ohm-m east of the fault, and 9 ± 3 ohm-m west of the fault. It is possible that the geothermal waters are fresher, and more resistive, than waters held in the lakebed clays. Water samples from more than 1 km depth in exploration wells have a TDS of 2500 p.p.m., nearly drinking-water quality. The relatively resistive water, perhaps localized by greater permeability along the fault, could explain the higher resistivity measured near the fault. The results show that there is no high-velocity, high-resistivity tufa along the faults below the surface, so we are unable to use buried tufa to locate the faults that may promote geothermal upwelling in this area. We further hypothesize that as sedimentation buried the tufa during the Quaternary, warm geothermal waters re-dissolved it, and re-precipitated it in the cold lake-bottom water.

15 GEOTHERMAL ENERGY↗

DOE OSTI2012

EMISSION MECHANISM OF 'GREEN FUZZIES' IN HIGH-MASS STAR-FORMING REGIONS

The Infrared Array Camera (IRAC) on the Spitzer Space Telescope has revealed that a number of high-mass protostars are associated with extended mid-infrared emission, particularly prominent at 4.5 {mu}m. These are called 'Green Fuzzy' emission or 'Extended Green Objects'. We present color analysis of this emission toward six nearby (d = 2-3 kpc) well-studied high-mass protostars and three candidate high-mass protostars identified with the Spitzer GLIMPSE survey. In our color-color diagrams, most of the sources show a positive correlation between the [3.6]-[4.5] and [3.5]-[5.8] colors along the extinction vector in all or part of the region. We compare the colors with those of scattered continuum associated with the low-mass protostar L 1527, modeled scattered continuum in cavities, shocked emission associated with low-mass protostars, modeled H{sub 2} emission for thermal and fluorescent cases, and modeled polycyclic aromatic hydrocarbon (PAH) emission. Of the emission mechanisms discussed above, scattered continuum provides the simplest explanation for the observed linear correlation. In this case, the color variation within each object is attributed to different foreground extinctions at different positions. Alternative possible emission mechanisms to explain this correlation may be a combination of thermal and fluorescent H{sub 2} emission in shocks, and a combination of scattered continuum and thermal H{sub 2} emission, but detailed models or spectroscopic follow-up are required to investigate this possibility further. Our color-color diagrams also show possible contributions from PAHs in two objects. However, none of our samples show clear evidence for PAH emission directly associated with the high-mass protostars, several of which should be associated with ionizing radiation. This suggests that these protostars are heavily embedded even at mid-infrared wavelengths.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2011

A Field Cancellation Algorithm for Constructing Economical Planar Permanent Magnet (PM) Multipoles With Large High Quality Field Apertures

In recent years studies have been initiated on a new class of multipole field generators consisting of cuboid planar permanent magnet (PM) pieces arranged in biplanar arrays of 2-fold rotational symmetry. These structures, first introduced for Free Electron Laser (FEL) applications, are based on reducing the rotational symmetry of conventional N-pole field generators from N-fold to 2-fold. One consequence of this reduction is a large higher-multipole content in a planar PM multipole's field at distances relatively close to the structure's axis, making it generally unsuitable for applications requiring a large high-quality field aperture. In this paper we outline an economical field-cancellation algorithm that can substantially decrease the harmonic content of a planar PM's field without breaking its biplanar geometry or 2-fold rotational symmetry. An economical field-cancellation algorithm has been described which will allow the fabrication of bi-planar quadrupoles and sextupoles with high-quality fields using a manageably small number of PM pieces. For higher order N-poles the number of pieces required to cancel a given number of successively-higher multipole components will also increase linearly; nevertheless, the practicability of fabricating octupoles and higher N-poles of this type should be considered a subject of continuing r&d. Since the removal of a large number of successive multipole components essentially increases the transverse region over which the N-pole's field is dominated by its leading N-pole field component, the fabrication of quadrupoles and sextupoles of the type described in this paper should lead to their introduction in storage ring applications. One potentially important application in this area is as distributed focusing elements installed into very-short-period, small-gap undulators (e.g., as a FODO lattice). The installation is rendered feasible by the very small vertical height of the biplanar N-poles (on the order of a millimeter), which, notwithstanding, doesn't prevent them from attaining focusing gradients on the order of several hundred T/m. If proven, this would allow short-period undulators of substantial length (viz., >>b) to be operated on storage rings, potentially transforming the optimality and economy of synchrotron radiation sources toward more favorable regimes.

43 PARTICLE ACCELERATORS↗

DOE OSTI2015

Performance of a GM tube based environmental dose rate monitor operating in the Time-To-Count mode

The events at the Fukushima Daiichi power plant in the aftermath of a natural disaster underline the importance of a large array of networked environmental monitors to cover areas around nuclear power plants. These monitors should meet a few basic criteria: have a uniform response over a wide range of gamma energies, have a uniform response over a wide range of incident angles, and have a large dynamic range. Many of these criteria are met if the probe is qualified to the international standard IEC 60532 (Radiation protection instrumentation - Installed dose rate meters, warning assemblies and monitors - X and gamma radiation of energy between 50 keV and 7 MeV), which specifically deals with energy response, angle of incidence, dynamic range, response time, and a number of environmental characteristics. EcoGamma is a dual GM tube environmental gamma radiation monitor designed specifically to meet the requirements of IEC 60532 and operate in the most extreme conditions. EcoGamma utilizes two energy compensated GM tubes operating with a Time-To-Count (TTC) collection algorithm. The TTC algorithm extends the lifetime and range of a GM tube significantly and allows the dual GM tube probe to achieve linearity over approximately 10 decades of gamma dose rate (from the Sv/hr range to 100 Sv/hr). In the TTC mode of operation, the GM tube is not maintained in a biased condition continuously. This is different from a traditional counting system where the GM tube is held at a constant bias continuously and the total number of strikes that the tube registers are counted. The traditional approach allows for good sensitivity, but does not lend itself to a long lifetime of the tube and is susceptible to linearity issues at high count rates. TTC on the other hand only biases the tube for short periods of time and in effect measures the time between events, which is statistically representative of the total strike rate. Since the tube is not continually biased, the life of the tube is extended and the linearity is greatly improved. Testing has been performed at Pacific Northwest National Laboratory (PNNL) in the USA and confirms compliance to IEC 60532 as well as linearity (± 10%) up to 100 Sv/hr. Furthermore, a network of EcoGamma probes may be linked through available supervisory software to provide a dose rate map of an area. This allows for real time monitoring of dose rates from one (or multiple) remote locations. (authors)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2015

KINEMATICS OF THE OUTFLOW FROM THE YOUNG STAR DG TAU B: ROTATION IN THE VICINITIES OF AN OPTICAL JET

We present {sup 12}CO(2-1) line and 1300 μm continuum observations made with the Submillimeter Array of the young star DG Tau B. We find, in the continuum observations, emission arising from the circumstellar disk surrounding DG Tau B. The {sup 12}CO(2-1) line observations, on the other hand, revealed emission associated with the disk and the asymmetric outflow related with this source. Velocity asymmetries about the flow axis are found over the entire length of the flow. The amplitude of the velocity differences is of the order of 1-2 km s{sup –1} over distances of about 300-400 AU. We interpret them as a result of outflow rotation. The sense of the outflow and disk rotation is the same. Infalling gas from a rotating molecular core cannot explain the observed velocity gradient within the flow. Magneto-centrifugal disk winds or photoevaporated disk winds can produce the observed rotational speeds if they are ejected from a Keplerian disk at radii of several tens of AU. Nevertheless, these slow winds ejected from large radii are not very massive, and cannot account for the observed linear momentum and angular momentum rates of the molecular flow. Thus, the observed flow is probably entrained material from the parent cloud. DG Tau B is a good laboratory to model in detail the entrainment process and see if it can account for the observed angular momentum.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2025

Spectroscopic Characterization of redMaPPer Galaxy Clusters with DESI

Optical galaxy cluster identification algorithms such as redMaPPer promise to enable an array of astrophysical and cosmological studies, but suffer from biases whereby galaxies in front of and behind a galaxy cluster are mistakenly associated with the primary cluster halo. These projection effects caused by irreducible photometric redshift uncertainty must be quantified to facilitate the use of optical cluster catalogues. We present measurements of galaxy cluster projection effects and velocity dispersion using spectroscopy from the Dark Energy Spectroscopic Instrument. Our findings are as follows: we confirm that the fraction of redMaPPer putative member galaxies mistakenly associated with cluster haloes is richness dependent, being more than twice as large at low richness than high richness; we present the first spectroscopic evidence of an increase in projection effects with increasing redshift, by as much as 25 per cent from $z\sim 0.1$ to $z\sim 0.2$; moreover, we find qualitative evidence for luminosity dependence in projection effects, with fainter galaxies being more commonly far behind clusters than their bright counterparts; finally, we fit the scaling relation between measured mean spectroscopic richness and velocity dispersion, finding an implied linear scaling between spectroscopic richness and halo mass. We discuss further directions for the application of spectroscopic data sets to improve use of optically selected clusters to test cosmological models.

clusters↗

DOE OSTI2012

OPACOS: OVRO POST-AGB CO (1-0) EMISSION SURVEY. I. DATA AND DERIVED NEBULAR PARAMETERS

We have performed interferometric observations of the {sup 12}CO (J = 1-0) emission in a sample of 27 objects spanning different evolutionary stages from the late asymptotic giant branch (late-AGB), through the post-AGB (pAGB) phase, and to the planetary nebula (PN) stage, but dominated by pAGB objects and young PNs ({>=}81%). In this paper (the first in a series) we present our maps and main nebular properties derived for the whole sample. Observations were performed with the Caltech Millimeter Array at the Owens Valley Radio Observatory. The angular resolution obtained in our survey ranges between 2.''3 and 10.''7. The {sup 13}CO and C{sup 18}O (J = 1-0) transitions as well as the 2.6 mm continuum emission have also been observed in several objects. The detection statistics in the {sup 12}CO, {sup 13}CO, C{sup 18}O transitions and 2.6 mm continuum are 89%, 83%, 0%, and 37%, respectively. We report first detections of {sup 12}CO (J = 1-0) emission in 13 targets and confirm emission from several previous marginal detections. The molecular envelope probed by {sup 12}CO (J = 1-0) emission is extended for 18 (out of 24) sources; envelope asymmetries and/or velocity gradients are found in most extended objects. Our data have been used to derive accurate target coordinates and systemic velocities and to characterize the envelope size, morphology, and kinematics. We also provide an estimate of the total molecular mass and the fraction of it contained in fast flows, lower limits to the linear momentum and to the isotopic {sup 12}C/{sup 13}C ratio, as well as the AGB mass-loss rate and timescale for sources with extended CO emission.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2014

New compact hohlraum configuration research at the 1.7 MA Z-pinch generator

A new compact Z-pinch x-ray hohlraum design with parallel-driven x-ray sources was experimentally demonstrated in a full configuration with a central target and tailored shine shields (to provide a symmetric temperature distribution on the target) at the 1.7 MA Zebra generator. This presentation reports on the joint success of two independent lines of research. One of these was the development of new sources – planar wire arrays (PWAs). PWAs turned out to be a prolific radiator. Another success was the drastic improvement in energy efficiency of pulsed-power systems, such as the Load Current Multiplier (LCM). The Zebra/LCM generator almost doubled the plasma load current to 1.7 MA. The two above-mentioned innovative approaches were used in combination to produce a new compact hohlraum design for ICF, as jointly proposed by SNL and UNR. Good agreement between simulated and measured radiation temperature of the central target is shown. Experimental comparison of PWAs with planar foil liners (PFL) - another viable alternative to wire array loads at multi-MA generators show promising data. Results of research at the University of Nevada Reno allowed for the study of hohlraum coupling physics at University-scale generators. The advantages of new hohlraum design applications for multi-MA facilities with W or Au double PWAs or PFL x-ray sources are discussed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗